The well-known antimicrobial activity of honey and its recent use in clinical settings has reinvigorated further investigation of bioactive honeys i.e., honeys marketed as having therapeutic potential.
Some honeys show broad-spectrum activity against antibiotic-resistant bacteria (Wang et al., 2012), while others are very effective against biofilm forming clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (Alandejani et al., 2009).
In conclusion this study has demonstrated that the non-peroxide activity of manuka honey is not exclusive to Australasia honeys, that it is not derived from hydrogen peroxide generation and may have a microbial origin.
Furthermore the action of manuka honey on Gram-negative bacteria seems to be more physical than in Gram positive where it appears to interfere with the cell physiology, perhaps by stopping the cell cycle before cytokinesis.
Gram-positive cells incubated in honey increased their endogenousre spiration rate whilst this was decreased in Gram-negative, major leakage was observed in Gram-negative bacteria whilst only minor leakage was observed in Gram-positive bacteria, which is consistent with the amount of damage observed with electron microscopy.
The proteome analysis of Staph aureus, revealed a general down regulation of protein synthesis.
No honey-resistant ram-positive bacteria were recovered, but Gramnegative bacteria were found to be able to become phenotypically resistant to manuka honey.
Electron microscopy showed that honey inflicted physical damages in both types of cells, and in Gram-positive bacteria led to an increase in the proportion of population of cells with a complete septum.
The chemical markers characteristic of Agastache honey and honeys of Leptospermum origin were phenyllactic acid and methyl syringate.
Overall, the bioactive compounds with antimicrobial and antioxidant activity in Agastache honey suggested a possible use for topical application and in wound care.